Algebraic Number Theory
《Algebraic Number Theory》 · 第 391 页 · Chapter VI，Section 5「The Global Reciprocity Law」，Theorem 5.5
§ 5. The Global Reciprocity Law. […] (5.5) Theorem. For every Galois extension $L/K$ of finite algebraic number fields we have a canonical isomorphism $r_{L/K}:G(L/K)^{\mathrm{ab}}\xrightarrow{\sim}C_K/N_{L/K}C_L$.